Wanna make a scope? Or better still, grind a mirror yourself. Or, you have some good tips in making a really useful accessory? This is the place to show what your hands can do...
They do have a catalog, but it's not online. Maybe you try to find at McMaster-Carr catalog first and email the picture and other details to Yong Seng to check?
Btw, I don't think they do mail order at the moment :-)